1. Field of the Invention
The present invention relates to the field of hydraulically operated clutch release bearings, particularly those intended to act on the diaphragm of a clutch, in particular for a motor vehicle.
2. Description of the Relevant Art
Clutch release bearings generally include a rolling-contact bearing one of the rings of which can rotate and the other ring of which is fixed. Between the rotating ring and non-rotating ring balls are arranged, these being uniformly distributed in the circumferential direction by means of a cage, the rotating ring being equipped with an attack surface intended to come into contact with the end of the fingers that make up the clutch diaphragm. An operating element supports the bearing and moves the thrust bearing axially against the clutch diaphragm.
An operating element includes a piston and means for axially securing the piston to the non-rotating ring. The piston is slideably mounted in an annular chamber of a cylinder fixed to the gearbox casing. The sealing between the piston and the cylinder is afforded by a seal in direct contact with the piston.
In some embodiments, the seal is fixed to the piston by a relatively complicated component—see document FR A 2 772 444. The cost of the component and of mounting it is high.
In other embodiments, the seal is not in any way angularly or axially connected to the piston. In this case, relative angular movements between the seal and the piston may occur both when the piston is being operated and when the piston is at rest in the clutch-engaged state, these movements perhaps being due to vibration and to an internal frictional couple between the rotating part and the non-rotating part of the bearing supported by the piston. Even if these angular movements are of small amplitude, their repetitive nature is likely to give rise to wear that is detrimental to the sealing of the device—see, for example, document FR-A-2 668 560.